Answer:
Incan Suspension Bridges - 6
While not necessarily easy to build, they are not much different from a standard hanging bridge.
Incan Terraces - 5
They are not easy to build whatsoever, but not that difficult either. This can be demonstrated by the fact that similar terrances can be seen in other regions of the world like China and Southeast Asia.
Aztec Chinampas - 4
They are basically floating plots of land, like a miniature version of modern day Dutch polders. They were a great feet of Aztec engineering.
Mayan Step-Pyramids - 3
Mayan Step-Pyramids are great feats of Mayan architecture and engineering, and professionals from this area still wonder at them.
Aztec Causeways - 2
This were the canals built in the lake of Texcoco, that connected the Aztec capital: Tenochtitlan, with its sorrounding.
Mayan Calendar - 1
A feat of Mayan mathematics, astronomy, and even numerology, the Mayan Calendar continues to wonder scientists to this day.
